Process of separating the 3, 5-dimethyl 1-ethyl benzene from other ethyl xylenes



Patented Feb. 13, 1951 UNITED TsTATEs PATENT OFFICE PROCESS OF SEPARATING THE 3,5-DI1WETH- YL 1ETIIYL BENZENE FROM OTHER ETHYL XYLENES William E. Elwell, Berkeley, Calif., assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware Application July 1, 1948, Serial No. 36,359

' zene, the 2,4-dimethyl l-ethyl benzene, and the 2,6-dimethyl l-ethyl benzene are, respectively, 183.75 C., 186.91o C., 188.41o C., and '189.75 C.

The present invention embodies the discovery that separation of the 3,5-dimethyl 1ethyl benzene from other ethyl xylenes such as the 2,4-dimethyl 1ethyl benzene, the 2,5-dimethyl l-ethyl benzene, and the 2,6-dimethyl l-ethyl benzene may be effected by rst sulphonating the ethyl xylenes and then subjecting the sulphonated mixture to hydrolysis preferably accompanied by simultaneous distillation. It app-ears that the sulphonated product obtained from the 3,5-di- `methyl l-ethyl benzene undergoes hydrolysis to reform the 3,5-dimethyl 'l-ethyl benzene readily at comparatively low temperatures and under conditions Where the products of sulphonation of the other ethyl xylenes do not undergo hydrolysis. It is thereby rendered possible to separate in substantial purity the 3,5-dimethyl -1-ethyl benzene from a mixture of the sameY with other xylenes by rst subjecting the admixture to sulphonation followed by a selective hydrolysis.

The process of the present invention, together with further objects andl advantages of the invention, will be fully understood from the follow: ing description of a preferred example of the invention as carried out in the apparatus illustrated in the accompanying drawings.

In the drawings the figure represents a diagrammatic View of a suitable apparatus in which the process of the present invention may be conducted, in which drawing, however, for the sake of clarity and simplicity, there have been omitted certain details, such as pumps, valves, measuring means, heat exchangers, coolers, reiiuxing apparatus, flow meters and like appurtenances, as will be readily supplied by one skilled in the art. Likewise, for a low corrosion loss of lines, vessels land columns, special materials of construction should be used. These are not referred to since they may be supplied by those skilled in the art without detailed instructions. K

In the process as illustrated in the drawings, a mixture of ethyl xylenesenters the sulphona- 2 tion vessel I through a line 2. Into the sulphonation vessel I there is introduced sulphuric acid through line 3. The sulphonation vessel I is preferably provided with a suitable stirring or agitating means such as is'indicated at 4, and

Y is jacketed as indicated at 5 for alternately heating and subsequently cooling the reaction mixture.

In the sulphonating vessel I suflicient concentrated sulphur-ic acid is added to effect sulphonation of all the ethyl xylenes introduced. `The strength ofv sulphuric acid used may be any strength usual in sulphonation, but I prefer/to employ sulphuric acid of a specific gravity of 1.84. The .sulphuric acid of such strength may,

-for example, be added to the ethyl xylenes in proportions of about 1.8 to one part by weight of acid to ethylxylene.A This is an excess of sulphuric acid over that required by the reaction, but an excess is desirable to' insure complete sulphonation of the reaction mixture.

The reaction may, if desired, be carried out in a batch process, under which conditions the ethyl .xylene is rst heated to a` suitable temperature,

such as about C., before the introduction of the Sulphuric'YaCid, whichis preferably gradually added for a suitable period of time, such as about an hour.y After the completion of the introduction of the sulphuric acid, it is preferable to raise the temperature of the reaction mixture somewhat, such as, for example, to C., and maintain it at an elevated temperature for a period of time such as 11/2 hours in order to insure completion of the sulphonation reaction.

After the completion of the sulphonation reaction, it is preferable to first cool the reaction mixture and then add a suitable quanti-ty of Water for effecting hydrolysis. The water may be introduced through the line 6. The amount of Water added is generally equal to about onethird or one-fourth of the weight of sulphuric acid employed. The mixture is then withdrawn from the vessel through a valve 'I and passed by line 8 into a still 9. In the still 9 the admixture is subjected to distillation to distill the water and the 3,5-dimethyl l-ethyl benzene formed by hydrolysis of the sulphonated mixture. The bulk of the material introduced into still 9 is removed at a temperature of about 114 C., but the distillation temperature may be carried up to a temperature of about C, at the end of the process. The Water and the 3,5-dimethyl l-ethyl benzene are removed from the still 9 as an overhead through a line I0.

The bottoms of the still are withdrawn from line II and consist of sulphonated ethyl xylenes derived from the ethyl xylenes other than the 3,5-dimethyl 1-ethyl benzene which were contained in the feed material introduced in line 2. The bottoms also may include tar. These bottoms may be disposed of as desired, but I have indicated the; bottoms as being withdrawn by line II and passed to a second still I2. In the still I2, by the use of high temperature and/or v sulphonating vessel I through line 2 may consist Y of any desired mixture of ethyl xylenes including the -dimeth-yl l-ethy-l benzene and any one or corrbination of any of the other ethyl xylenes includ-ing the 2,4-dimethyl I-ethyl benzene. the 2,5-dimethyl 1-ethyl benzene.. and the 2.6-dimethyl 1ethyl benzene. process of the present invention, in one operation of the process the ethyl xylene admixture ied to the sulphonation vessel I through line Z constituted an admixture analyzing substantially 47% of the 3,5-dimethyl l-ethyl benzene. 39% of the 2,4-dimethyl 1-ethyl benzene, 11% of the 2.6- dimethyl l-ethyl benzene, and 3% ofthe 2,5-dimethyl l-ethyl benzene. This ethyl xylene admixture was subjected to the process at substantially the conditions previously given. When the suphonated product was subi'ected to hydrolysis and distillation in the still. two cuts were taken continuously and analyzed for density and refractive index. The density of the ethyl xylene cuts obtained from line Iii of the condensate remains sub"tantiallv constant at about the density of 0.864% and refractive index ot' 1.4980, which are the denfitv and refractive index of the desired 3,5-dimetbyl l-ethyl benzene, until substantially the complete recovery of this product has been effected, thus establishing that this component of the mixture was capable of being separated in substantial purity in the process from the other ethyl xylenes of the admixture process.

While the particular example of the process D herein described is well adapted to carry out the objects of the invention. it is toghe understood that various modifications of the process may be employed and this invention is of the scope set forth in the appended claims.

I claim:

1. A process of separating the 3.5-dimethyl 1- ethyl benzene from other ethyl xylenes, including the ZA-dimethyl 1-ethyl benzene, the 2,5-dimethyl l-ethyl benzene, and the 2,6-dimethyl lethyl benzene, which process comprises subiecting a mixture of the 3,5-dimethyl l-ethyl benzene and at least one such other ethyl xylene to a sulphonating reaction with sulphuric acid in which substantially all of the ethyl xylenes in the mixture are sulphonated, thereafter adding water and subjecting the sulphonated reaction mixture to hydrolysis in which the sulphonated product of the 3,5-dimethyl 1-ethyl benzene is hydrolyzed while the other sulphonated ethyl xylenes remain substantially unhydrolyzed the temperature of hydrolyzation being below about 160 C., and separating such ethyl xylene from the sulphonated materials.

As, an example of the 2. A process of separating the 3,5-dimethyl 1- ethyl benzene from mixtures with other ethyl xylenes, including the 2,4-dimethyl l-ethyl benzene, the 2,5-dimethyl l-ethyl benzene, and the 2,6-dimethyl l-ethyl benzene, which comprises reacting a mixture of such 3,5-dimethyl l-ethyl benzene and at leastone other of such ethyl xylenes with sulphuric acid in order to sulphonate substantially all the ethyl xylenes, then adding water and subjecting the sulphonated reaction mixture to hydrolysis so as to hydrolyze substantially only the sulphonated material derived from the 3,5-dimethyl l-ethyl benzene the temperature of hydrelyzation being between about 114 C. and C. anddistilling such ethyl xylene from the remaining unhydrolyzed sulphonated material.

3. A method of separating the 3,5-dimethyl 1- ethyl benzene from mixtures of the group of ethyl xylenes including the .2A-dimethyl l-ethyl benzene, the 2,5-dimethyl 1-ethyl benzene, and the l-dimethyl 1-ethyl benzene, which comprises sulphonating substantially entirely an admixture of the :3b-dimethyl 1ethyl benzene with at least one. of such other xylenes by reaction with sulphuric acid, thereafter hydrolyzing the sulphonated mixture by the addition of water at a temperature below the hydrolyzation temperature of the sulphonated materials other than the sulphonated 3,5-dimethyl l-ethyl benzene, and hydrolyzing said latter material the temperature of hydrolyzation being below about 160 C. and separating such ethyl xylene from the sulphonated materials.

4. A method of separating the i5-dimethyl 1- ethyl benzene from mixtures of the group of ethyl xylenes including the ZA-dimethyl 1ethyl benzene, the 2lb-dimethyl l-ethyl benzene, and the 2,6-dimethyl 1ethyl benzene, which comprises sulphonating substantially entirely an admixture of the 3,5-dimethyl l-ethyl benzene with at least one of such other xylenes by the addition of reaction with sulphuric acid, thereafter hydrolyzing the sulphonated mixture by the addition of water at a temperature below the hydrclyzation temperature of all but the sulphonated 3,5-dimethyl l-ethyl benzene, hydrolyzing said latter material from the sulphonated residue the temperature of hydrolyzation being between about 114 C. and 166 C., and separating the same by distillation from the sulphonated residue.

5. A method of separating the 3,5-dimethyl 1- ethyl benzene from mixtures oi the group of ethyl xylenes including the lll-dimethyl 1-ethyl benzene, the 2,5-dimethyl l-ethyl benzene, and the 2,6-dimethyl l-ethyl benzene, which comprises suiphonating substantially entirely an admixture oi the 3,5-dimethyl 1-ethyl benzene with at least one of such other xylenes by reaction with sulphuric acid, thereafter hydrolyzing the sulphonated mixture by the addition of water at a temperature below the hydrolyzation temperature of all but the sulphonated 3,5-dimethyl 1- ethyl benzene, and separating by hydrolyzing said latter material from the sulphonated residue, the temperature of hydrolyzation being below about 160 C.

6. A method of separating the 3,5-dimethyl 1- ethyl benzene from mixtures of the group of ethyl xylenes including the 2,4-dimethyl l-ethyl benzene, the 2,5-dimethyl l-ethyl benzene, and the .1G-dimethyl l-ethyl benzene, which comprises sulphonating substantially entirely an admixture of the 3,5-dimethyl l-ethyl benzene with at least one of such other ethyl xylenes, thereafter simultaneously hydrolyzing and distilling the lower 5 boiling fraction consisting principally of 3,5-dimethyl l-ethyl benzene from the sulphonated residue, the'A temperature of hydrolyzation and distillation being below about 160 C.

7. A method of separating the 3,5-dimethyl 1- ethyl benzene from mixtures of the group of ethyl xylenes including the 2,4-dimethyl l-ethyl ben-V zene, the 2,5-dimethyl l-ethyl benzene, and the 2,6-dimethyl l-ethyl benzene, which comprises sulphonating substantially entirely an admixture of the 3,5-dimethyl l-ethyl benzene with at least one of such other xylenes by reaction with about 1.8 parts by Weight of concentrated sulphuric acid to about 1 part by weight of ethyl xylene admixture, thereafter hydrolyzing the sulphonated 'mixture by the addition of water equal to from about 1/4 to 1/3 of the Weight of sulphuric acid at a temperature below the hydrolyzation temperature of all but the sulphonated v3,5-dimethyl 1ethyl benzene, and separating by hydrolyzing said latter 20 material from the sulphonated residue, the tem- REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Cole et al May 9, 1944 Number 

1. A PROCESS OF SEPARATING THE 3,5-DIMETHYL 1ETHYL BENZENE FROM OTHER ETHYL XYLENES, INCLUDING THE 2,4-DIMETHYL 1-ETHYL BENZENE, THE 2,5-DIMETHYL 1-ETHYL BENZENE, AND THE 2,6-DIMETHYL 1ETHYL BENZENE, WHICH PROCESS COMPRISES SUBJECTING A MIXTURE OF THE 3,5-DIMETHYL 1-ETHYL BENZENE AND AT LEAST ONE SUCH OTHER ETHYL XYLENE TO A SULPHONATING REACTION WITH SULPHURIC ACID IN WHICH SUBSTANTIALLY ALL OF THE ETHYL XYLENES IN THE MIXTURE ARE SULPHONATED, THEREAFTER ADDING WATER 